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Mouse Sperm Kept In Space Can Still Produce Offspring

June 8, 2017

Written byCuriosity Staff

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Next stop, generation ship: mouse sperm that had been stored in space for nine months successfully gave rise to healthy baby mice. That suggests that reproduction in space isn't as hazardous as we thought, and could mean that a permanent space civilization is a possibility for the human race.

What Happens In Space Stays In Space

Sex in space. We've all thought about it. (Don't leave us hanging here). You've got microgravity, an excess of alone time, and the beauty of stars and planets all around you. The problem is that sex can lead to pregnancy, and pregnancy in space is a risky proposition. You see, in space, you don't have Earth's magnetosphere to protect you from high-energy particles known as cosmic rays, which deliver ionizing radiation that can damage DNA and lead to things like genetic mutations and cancer. Astronauts on the International Space Station, for example, are exposed to 100 times more radiation than they are on Earth. That radiation could do untold things to a developing fetus, or even to the astronauts' eggs and sperm before they've had a chance to fertilize.

But the key there is "untold." Most studies of mouse reproduction in space have focused on the effects of gravity—mouse pups born in space tend to have lower birth weight and a higher risk of death. And sure, astronauts also suffer ill effects from weightlessness, including impaired vision and a weakened heart. But assuming we invent some sort of artificial gravity for the spaceships of the future, we'd still need to address the danger of space radiation on our offspring. That's where an experiment with freeze-dried space sperm comes into play.

ISS Stands For Indestructible Space Sperm

In a study published in the Proceedings of the National Academy of Sciences in 2017, researchers describe the process that led to a litter of healthy mouse pups being born from sperm preserved in space. They collected samples of mouse sperm and freeze-dried it—an unusual process for sperm, since most animals' sperm can't survive freeze drying and is better maintained using cryopreservation. Cryopreservation requires the cost and weight of a freezer, however. And anyway, freeze-dried mouse sperm does survive, "and this may possible with human spermatozoa in the future," the authors write. They then sent the freeze-dried sperm up to the International Space Station, where it was stored for 288 days, or roughly nine months.

Once the sperm was returned to Earth, the researchers examined it and found that it had experienced some DNA damage. Uh oh. Nevertheless, they used the sperm to perform in vitro fertilization and produce embryos that they then transferred into female mice. What happened? As Space.com explains, "The average birth rates from the two kinds of samples were comparable, and the ratio of male to female in the two kinds of pups fell within the normal range, the researchers said. Furthermore, analyses of the pups' genomes revealed only minor differences between the two types of mice, and the pups from space-preserved sperm went on to develop into adults with normal fertility." Researchers think the DNA damage they saw may have been repaired after fertilization, since past research shows that egg cells have that ability.

The fact that mice successfully reproduced using freeze-dried sperm doesn't just mean exciting things for space travel. It could be a game changer for beings on Earth, too. If we can figure out how to preserve sperm of other animals using the same methods, we might be able to create a sort of doomsday sperm vault akin to what Norway's Svalbard Seed Vault does for plant species. Either way, the survival of our species is looking better and better.